Glomerular filtration

Glomerular filtration is the movement of water and small solutes from blood in glomerular capillaries into the nephron, while most cells and large proteins remain in the blood.

Glomerular filtration barrier: A layered interface of fenestrated endothelium, basement membrane, and podocyte slits that filters plasma into Bowman’s space. Its layers determine which components of capillary blood cross into the nephron.
Nephron: The kidney’s functional unit, consisting of a renal corpuscle and a tubule that modifies filtrate. Glomerular filtration begins the nephron’s processing of blood-derived fluid.
Creatinine clearance: An estimate of glomerular filtration rate based on urinary creatinine excretion and plasma creatinine concentration. It uses renal handling of creatinine to estimate filtration in practice.
Tubular reabsorption: The movement of water and solutes from nephron fluid back into the blood. Unlike filtration, it returns selected substances from the tubule to circulation.
Glomerular capillary hydrostatic pressure: The blood pressure within glomerular capillaries that pushes fluid across the filtration barrier. It supplies the main outward force driving filtration.
Renal corpuscle: The kidney structure formed by a glomerulus enclosed by Bowman’s capsule. This is the anatomical site where filtration produces tubular fluid.
Estimated glomerular filtration rate: A calculated estimate of glomerular filtration rate derived from blood markers and patient characteristics. It translates filtration-related blood measurements into a routine kidney-function estimate.
Tubular secretion: The movement of substances from blood into nephron fluid across tubular epithelium. It adds substances to tubular fluid after the glomerulus has filtered plasma.
Bowman's capsule: The cup-shaped nephron structure surrounding the glomerulus that collects newly filtered fluid. Filtrate enters its space immediately after crossing the capillary barrier.
Glomerulus: A tuft of capillaries within the renal corpuscle that filters blood plasma. Its capillaries expose plasma to the filtration barrier.

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